1. Field of the Invention
The present invention relates to a semiconductor device having capacitors and a method of manufacturing the semiconductor device.
2. Description of the Related Art
In recent years ferroelectric memories such as ferroelectric random access memories (FeRAMs) have been developed. A ferroelectric memory comprises capacitors each having a ferroelectric film used as dielectric film.
A ferroelectric memory has been proposed in which the ferroelectric film is a PZT (Pb(ZrxTi1-x)O3: 0<x<1) film and the bottom electrode and top electrode are SRO (SrRuO3) films. (See, for example, U.S. Pat. No. 6,351,006 and U.S. Pat. No. 6,194,228.) This structure can improve the fatigue characteristic of each capacitor incorporated in the ferroelectric memory.
However, the elements contained in the PZT film are different from those contained in the SRO film, except oxygen. Therefore, electric charge is likely to accumulate in the interface between the PZT film and the SRO film. The capacitor may therefore be deteriorated in terms of retention characteristic and imprint characteristic. If the SRO film is formed by sputtering, its crystal orientation will be at random. Hence, any PZT film formed on the SRO film inevitably has random crystal orientation, due to the random crystal orientation of the SRO film. Accordingly, the capacitor cannot undergo so prominent polarization as is desired.
Conventional capacitors, each having a PZT film used as ferroelectric film and SRO films used as electrode films, undergoes but insufficient polarization and may be deteriorated in retention characteristic and imprint characteristic. It has been difficult to provide capacitors that are as reliable as desired and have good characteristics.